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ORIGIN: United States

Extension Goat Handbook

This material was contributed from collections at the National Agricultural Library. However, users should direct all inquires about the contents to authors or originating agencies.

DOCN 000000032
NO D-6
E. L. Bliss; U. of Florida, Gainesville E. A. Oltenacu; Cornell U., Ithaca, NY R. S. Ott; U. of Illinois, Urbana S. B. Guss; Pennsylvania State U., University Park
Genetics and Reproduction

1 The reproductive performance of goats can be exceptionally high. Conception rates of 980ver 2 estrous cycles with an average of 1.5 kids have been reported. Such fertility is probably due to maximizing proper management. Reproductive management of dairy goats involves three periods: the breeding season, the pregnant and dry period; and kidding time.

2 The Breeding Season Yearling kids may be bred in the first year at 7-10 months of age, depending on breed, if they have grown well to about 80 lb and are of good size and condition. Body weight relative to breed is more important than age and can influence lifetime performance. The doe kid may be able to reproduce at three months of age but should not be allowed to do so, as her growth may be permanently stunted. To prevent this, buck kids should be separated from doe kids at an early age. If breeding doe kids is postponed much beyond 10 months of age, they will be less productive. Older kids are not as easily settled at first breeding and may have lower lifetime productivity.

3 Breeding does, as the season approaches should be ''flushed'', i.e. prepared by having them gain weight at least 2-3 weeks before breeding. This increases the number of ovulations. Records should be kept carefully on all heats, lengths of heat, intervals between heats and all breeding dates. Most goats are seasonal breeders, and their season is initiated by decreasing daylight. Thus, their season is from late August through January usually, but tropical breeds of goats may cycle year around.

4 Seasonal breeding results in seasonal peaks and valleys of milk production which makes it difficult to maintain a level fluid milk market. However, goats can be milked longer than the standard 305-day lactation by delaying breeding to a later heat. Goats can also be ''fooled'' into thinking that the short-day season has arrived by manipulating artificial light-hours per day and thereby initiating estrous cycles out-of-season. However, this requires an investment in housing which is suitable for light control.

5 Hormonal reproductive problems are not common in goats. Cystic ovaries may occur, usually late in the breeding season. These are a hereditary problem and show up in young animals. The signs of cystic ovaries are constant heat, male-like behavior, or frequent short cycles. Treatment may consist of giving hormones: luteinizing hormone containing compounds (3,000 IU/im) or progesterone in oil (100mg/d for 12 days). Young does with cystic ovaries probably should not be bred and be culled, to prevent the continuation of this condition.

6 Anestrus (no heats) can be a problem. This may be due to: a pregnancy from an unobserved service, if a buck is present; intersexed goats which are not discovered until examined to determine why they are not cycling; the inability to observe does in heat; or simply not cycling. Close observation and understanding the signs of estrus is the best way to determine when the doe is in heat. Signs of heat (estrus) are: swelling and redness of the vulva: mucus discharge (may become white toward the end of estrus); tail twitching; increased bleating (vocalization); decrease in milk production; increased restlessness; and frequent urination. Standing or riding are not seen as heat signs in goats as often as in cows. Observation around feeding and milking times is undesirable, because the does have their mind not concentrated on est ++++MISSING DATA++++

7 Estrus (heat) lasts from 12 to 48 hours, averaging 36 hours and ovulations occur 24 to 36 hours after onset of heat. Goats should be bred naturally once 24 hours after onset of heat or if conservation of the buck is not a consideration, every 12 hours until the receptive period is over. In artificial insemination, it is recommended to breed every 12 hours, 2 to 3 times. Does generally have heat cycles of 21 day length, similar to cows. However, considerable variation between individual does exists without any abnormality reason. The recurrence of estrus cycles should be fairly consistent in an individual animal. A doe with an unusual cycle length of 35 to 40 days should be suspected of embryo loss and should be placed under careful observation.

8 A buck must be prepared for the breeding season with good nutrition, parasite control, foot trimming, etc. A prebreeding genital exam should be carried out with examination of the testicles for any abnormalities. The testicle should be plump, firm and symmetrical. If any abnormalities or problems are suspected, a semen evaluation should be carried out. Many systemic debilitating diseases, arthritis, foot rot, and scrotal infections can affect fertility of bucks.

9 The Pregnant Doe Pregnancy diagnosis should be done to ensure pregnancy has occurred and if not, the situation corrected before the end of the season. Gestation in goats is 150 days. Pregnancy diagnosis continues to be a problem in small ruminants. Nonreturn to estrus is the most commonly used sign of pregnancy. This requires close observations and can be adequate. If a buck is present, return to estrus determination is simple.

10 Recto-abdominal palpation with the aid of a rectal probe can be done with great caution and experience from 70 to 110 days but many veterinarians find it too dangerous to recommend. After 110 days the fetuses can be palpated through the abdominal wall. Ultra sound and radiography pregnosticators are available but the initial expense is a limiting factor.

11 Milk tests, e.g. available from DHIA labs, can be used at 21 to 23 days post-breeding to detect levels of the pregnancy hormone, progesterone. Low levels indicate a non-pregnant status. However, goat owners should keep in mind that an animal detected as pregnant may later lose the fetus, because goats may be more susceptible to abortion than cows, particularly during the periods of poor nutrition.

12 Contagious reproductive diseases are not a common problem in goats. Brucellosis caused by B. melitensis is not found in the United States although it is a problem in other parts of the world. Goats are resistant to Brucella abortus, the brucellosis of cows and it is not a problem. Enzootic abortion, a chlamydial infection, occurs in California and causes abortions. Characteristically 80 percent of abortions occur in first and second fresheners and 3 to 4 weeks before normal kidding. Natural immunity develops and vaccination programs are effective in problem areas. Whenever an abortion occurs, careful examination of the aborted fetus(es) and placenta is essential by submitting to a diagnostic pathology laboratory.

13 The Dry Doe The pregnant doe should have a 60 day dry period prior to kidding and should be gaining in condition for the last month before kidding without fattening. Nutrition must be carefully managed to provide the necessary nutrients balanced so that no metabolic disorders such as ketosis and milk fever may occur. About four and two weeks prior to kidding an intramuscular administration of a selenium treatment (Bo-Se) at the rate of 1 ml per 40 lb of bodyweight is advisable in selenium deficient areas such as the Northeast, Mid-Atlantic, Great Lakes, East Coast, Florida, and Northwest areas in the US.

14 The Kidding Doe (Parturition) Attendance at kidding is life saving and cleanliness is very important. The fetus acquires the capacity for extrauterine life only shortly before term, and may die in utero if parturition is unduly delayed. As kidding time approaches, the udder rapidly enlarges, the pelvic ligaments relax around the tail head, and the vulva becomes greatly enlarged. Eight to 12 hours before birth, the cervix begins to dilate and the cervical mucus plug will be in evidence, as a tan, sticky substance smeared about the hind parts of the doe. This first stage of kidding lasts 1 to 6 hours. If progress stops, a vaginal exam with clean, well lubricated hands is in order.

15 Normally the fetus enters the birth canal and the doe starts an abdominal press. The chorioallantoic sac is ruptured and the unbroken amniotic sac (water bag) is then forced through the vulva. Delivery of the kids usually occurs in a short time once the water bag can be viewed. Kids may be presented either with their front feet forward or in posterior presentation where their rear feet are presented first. The doe may rest between each kid for a short period of time. Most does are best left alone during parturition. Interference with parturition of does kidding for the first time may result in the doe rejecting the kids. It is important that does lick the kids as soon as possible after they are born as this indicates her acceptance of them. Dystocias (difficult births) are rarely encountered.

16 If labor is prolonged for more than one hour with no progress, a vaginal exam is again indicated. With multiple births, more than one fetus may be lodged in the pelvis. Careful sorting is necesary before delivery is possible. The goat's uterus is very fragile and prolonged manipulation may result in uterine rupture. ''Ring womb'' occurs, when, with prolonged labor, the cervix begins to contract, making delivery impossible. Caesarean sections are done with overlarge fetuses, monsters, ''Ring womb'' and other dystocia that might threaten the doe's life.

17 After parturition, the doe should begin to lick the kids, and she may eat part of the fetal membranes. There is no evidence for benefit or harm from ingestion of the fetal membranes. Normal kids will start trying to stand up immediately and should be on their feet and nursing within a short period of time. It is important that kids nurse the doe as soon as possible after birth in order to get the first milk or colostrum. It may be necessary occasionally to help slow or weak kids to nurse. Kids navels should be dipped in iodine solution. Retention of the fetal membranes, a condition not uncommon in cows, seldom occurs in goats. A retained placenta should be treated conservatively with the exposed portions clipped off. The placenta is discharged naturally 3-5 days if not normally expelled within 6 hours after kidding. Systemic antibiotics are indicated only if the doe shows signs of illness.

18 Thorough disinfection of pens after each delivery and especially after problems is important for successful reproductive management. Tetanus toxoid and enterotoxemia C and D bacterin injections are advised after each delivery as well as deworming. Colostrum feeding should be continued to kids beyond the first hours after kidding for three days. Excess colostrum can be frozen successfully for later use in other kiddings. The fresh doe will normally discharge a deep red, mucus-like material called lochia for 7 to 14 days postpartum. Abnormal is a large amount of bright red blood, foulsmelling exudate, or pus.

19 The Intersex The most important cause of infertility in dairy goats is the occurrence of the hermaphroditism or intersex condition. Affected animals are more frequently female genetically with a normal female complement of chromosones (60,XX). They may have a normal size vulva but an enlarged clitoris and a short or atretic vagina. A penile clitoris or even an ova testis may occur in does that appear phenotypically female otherwise. A shortened penis, hypospadias, or hypoplastic testes may also occur.

20 Both hermaphroditism and congenital hypoplasia of the reproductive tract are related to naturally hornless or polled goats and are more likely to occur when both parents are polled. Breeding to horned bucks will avoid the problem but breeding to horned does can reduce the occurrence of intersex sterility also. Breeding polled bucks to polled goats may result in a shift to more males born and as many as 20 hermaphroditic progeny. Hornlessness acts as a simple dominant and intersex sterility may be its pleiotropic effect on a recessive trait with incomplete penetrance, although linkage has not been excluded. The polled gene has a high frequency in Saanen but is rare in Angoras. The management interest in absence of horns needs to be balanced against losses due to intersex and labor costs in manual dehorning.

21 Since hornlessness is dominant over horned condition, it is of management value to be able to distinguish phenotypically the heterozygous goats from the homozygous polled animals. Recent French studies have demonstrated that small differences in the shapes and positions of the bony rudimentary hornknobs can be identified in goats. For homozygous polled males they are rounded and separate, while in heterozygous goats the two knobs are of oval shape and in a partially joined V-shaped position.

ORIGIN;United States


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